Blending a fibrous filler such as a glass fiber and a carbon fiber is commonly known to improve mechanical properties of thermoplastic resins. In general, a method is used in which a thermoplastic resin and chopped strands (staple fibers) of a fibrous filler are melt-kneaded in an extruder to produce a fiber-reinforced resin composition.
In recent years, however, there has been an increased demand for higher-performance plastics and rigidity comparable to that of metals. To achieve rigidity comparable to that of metals, it is necessary to fill a fibrous filler in large amounts and maintain a long fiber length, but methods in which a common fibrous filler is used for melt-kneading in an extruder had many problems. For example, fibers are broken by shearing during melt-kneading; resin is degraded by shear heating due to the fibrous filler; and when carbon fibers are blended in large amounts, the internal pressure of a die of an extruder increases, and fluffing of strands occurs, resulting in unstable production. Methods in which a thermoplastic resin and a fibrous filler are melt-kneaded in an extruder provided limited increase in performance.
In response, resin compositions have been proposed in which a nylon resin is blended with a specific carbon fiber to achieve weight saving and higher rigidity (JP 2006-1964 A and JP 2006-1965 A).
JP 2003-238818 A proposes a carbon fiber-reinforced thermoplastic resin composition comprising a thermoplastic resin, carbon fiber, and titanium oxide, and discloses a long fiber-containing thermoplastic resin composition in which the carbon fiber is covered with a thermoplastic resin preliminarily compounded with titanium oxide. According to that method, the fiber length can be kept long, and excellent properties can be exhibited.
Further, JP 2000-109671 A proposes a resin composition comprising a specific polycarbonate resin and a fibrous filler, and discloses a polycarbonate resin composition containing carbon fibers in an amount of about 30%.
For the resin compositions disclosed in JP '964 and JP '965, weight saving and higher rigidity are achieved through the use of a carbon fiber, but there is a problem with appearance/designability in that undulating irregularities tend to occur, resulting in significantly deteriorated appearance. Further, a method in which a carbon fiber is blended in an amount exceeding 40% by weight is not disclosed.
For the resin composition disclosed in JP '818, the amount of a carbon fiber is limited, and the amount exceeding 30% by weight is not described.
The resin composition disclosed in JP '671 provides insufficient properties and insufficient productivity.
As described above, for thermoplastic resin compositions, various approaches have been attempted in raw materials such as polymer raw material and fibrous filler. However, there is no known technique that achieves high rigidity and provides a resin composition having excellent appearance/designability.
It could therefore be helpful to provide a carbon fiber-reinforced thermoplastic resin composition having excellent mechanical properties and appearance/designability, and a molded article produced by molding the same.